Apparatus for fractionating cracked products



June 27, 1933. E, w LUSTER APPARATUS FOR FRACTIONATING CRACKED PRODUCTSFiled March 29, 1950 narvlrlviii v lu INVENTOR ATTORNEY Patented June27, 1933 t UNITED "STATES PATENT oFFicE ERIC w. DUSTER, or w sTrIELnnEwJERSEY, Assreivonro STANDARD orn DEVELOPMENT COMPANY, A CORPORATION orDELAWARE "AIVPVPARATU'S non FRAC'IIQNATING 'oRAoxEnrRoDUo'rs V 7Application filed March 29, 1930. Serial No. 439,953.

This invention relates to an apparatusfor separating cracked productsinto their constituents. Itmay beused in connectionwith liquid and vaporphase cracking processes although usually it can be employed with moreadvantage inr'connection with liquid phase cracking processes. I A mainobject of the present invention is toallowtthe simultaneoussupply offresh 10 feed oil to the bubble tower ofjthe cracking system and thewithdrawal of heavy uncracked products unmixed with fresh-feed from thesame bubbletowerm Another object is to allow the withdrawal of heavyresidual products from. the bubble tower into which fresh I gas .oil or'other charging stock,,is fed, without drawing off charging stock andthereby losing part of the conversionduring the. cracking operation. 1

Another object is to provide an apparatus for carrying out suchaprocess.

I Other objects and advantages will become apparent during the followingdescription 2 read in conjunction with the drawing, which is a verticaldiagrammatic section through the bubble tower constructed according tothe invention.

V It is common practice in cracking operations, to discharge the feedoil into direct contact with hot cracked vapors, so that it finallycollects atthe bottom of a tower freed from lower boiling fractions andis pumped therefrom, together with the heavy residual products, to thecracking equipment. I

The direct contact has the disadvantage that in the case where it isdesired to remove from the system part of the heavy residual products,it has not been possible to do this without simultaneously removing acertainv portion of the fresh gas oil or other charg- .ing stock, whichis mixed with the heavy products. This, however, is not desired be- 7cause the fresh gas oil is a better cracking stock thanthe heavyproducts which have already gone through the cracking coil and soakingdrum and therefore consist of hydrocarbons more resistant todecomposition than fresh gas oil. I have discovered a method and devisedan apparatus which will cracking coil.

be described jointly and which eliminate the disadvantage justdiscussed.

In the figure, the numeral 'l'designates a bubble tower into which thecracked hydrow carbon oil largely in vapor form, from which the tar hasbeen eliminated, isvdischarged through line .2. The bubble tower,comprises a shell which is divided into several compartments by means ofa number of perforated plates 3 on which bell caps and reflux lines arearranged. A partition wall 4 is-provided in'the middle sectionof thebubs bletower', running through several compartmentsand dividing theminto passageways. The partition wall may be flat, in which case 05 eachcompartment is divided into two half: cylindrical sections, or it may becircular, in

which case each'compartment is divided into a cylindric alj and anannular section. The partition wall may, however, have any other '7suitable shape. It divides the shellinto upwardly extending inlet andoutlet passage:

ways opening at top and .bottom into the shell. V

' The fresh gas oil may be fed through line 5 to cooling coils 6arranged in the upper part of the'bubble tower and then dischargedthrough line 7 into theuppermost compartment of the inlet-passage whichhas been formed by the partition wall. The gas oil comes here intodirect contact with the stream of vapors passing upward and causes thecondensation of the heavier products and at the same time becomes itselffurther preheated. After leaving the last compartment which is providedwith a partition wall the gas oil commingles with the heavyresidualproducts returned to the lowest plates through the reflux lines. Themixture of fresh gas oil andheavy residual'products finally accumulatesat'the bottom ofthe tower and is passed therefrom through line 8 to theI The light products leave the A tower through line 9 and are introducedeither into a final condenser or into a secondary '95 bubble tower,forthe purpose of further frac- I tionation.

From the compartment which is just above the partition wall the refluxedliquid is returned by reflux line 11 to the uppermost compartment of theoutlet passage and which does not come in contact with fresh gas oil.This reflux, which consists of heavy residual products, is finallyreturned to the lower compartments without partition walls. One of thecompartments of the outlet passage, for example the lowest one, isprovided with a valved line 12 through which part of the heavy residualproducts may be eliminated from the system. It is obvious that suchproducts will not be mixed with fresh gas oil. The product eliminatedthroughline 12 may be used for various purposes such as for instance,Diesel oil, or it may be mixed with the tar to control the gravitythereof and the mixture used as fuel oil.

It will be obvious that the fresh gas oil may be discharged into thesecondary bubble tower instead of being discharged into the primarybubble tower. The operation of the secondarybubble tower is in this casesimilar to the one just described but the product removed through line12 is lighter. It is usually passed through another vessel in which itis stripped from the light products by m'eans of open steam and isused,after cooling, as furnace oil.

In. a unit charging 10,000 gals. of gas oil per hour of total feed, thefresh feed may var from 25 to 100% of the total feed, but is usually toThe temperature of the oil at the outlet end of the heating coil may befor example 880 F. I The amount of heavy gas oil or DieselOll'WlilllClliLV/D F0111 the tower may vary from 10 to 30% of the totalfeed. The temperature of the stocks so withdrawn will be from 600 to700E, being higherfor the lowest percentage of fresh feed The pressure onthe tower will be from atmospheric to 175#, but in general will bebetween and per square inch.

Having thus described my invention what I claim is the following:

1. A fractionating tower comprising a shell, means dividing anintermediate portion of the shell into upwardly extendingnon-communicating inlet and outlet passageways opening at top and bottominto the shell, the tower including perforated plates with bell caps andreflux lines, the plates extending transversely of the shell above andbelow the passageways and through the passageways, means for introducinghydrocarbons into the tower below the passageways, means for introducingfresh feed oil into the inlet passageway, means for withdrawing refluxcondensate from the outlet passageway of the shell, and an outlet at thetop and bottom of the tower. a

- 2. A fractionatingtower according to claim 1, in which the means forintroducing fresh feed oil into the inlet passagewayopens into the upperportion of the inlet passageway and in which the means for withdrawingreflux condensate from the outlet passageway of the shell leads from thelower portion of theoutlet passageway. r r

3-. A fractionating tower according to claim 1, in which the means fordividing the intermediate portion of the shell is a substantiallyvertically disposed partition extending transversely of the shell.

4. A fractionating tower according, to

claim 1, in which the means for introducing fresh feed oil into theinlet passage leads 3 through the upper portion of the tower wherebyindirect heat exchange of the fresh feed oil and the tower contents iseffected.

ERIC W. LUSTER;

